Here the fall of the potentiometer along the length of the potentiometer wire … Measurement of emf of commercial cells using... Potentiometers are the devices that measures the potential difference without consuming much power fom the system. These potentiometers are used in huge quantities in the manufacture of electronics equipment that provides a way of adjusting electronic circuits so that the … The potentiometer is used as a precision divider. Aim: To determine the internal resistance of a given primary cell using cell using potentiometer .. The error in measurement is found by comparision with readings of potentiometer. (b) Figure shows the circuit diagram of a potentiometer for determining the emf ‘ ε ’ of a cell of negligible internal resistance. $\frac{E_{1}+E_{2}}{E_{1}-E_{2}}=\frac{6}{2}$ or $\frac{E_{1}}{E_{2}}=\frac{2}{1}$, Keeping $\mathrm{K}_{1}$ open the balancing length $\ell_{1}$ gives, Keeping $K_{1}$ closed the balancing length $\ell_{2}$ for some resistance R gives potential difference so V = $x \ell_{2}$, Internal resistance $r=\frac{E-V}{V} \quad R=\frac{x \ell_{1}-x \ell_{2}}{x \ell_{2}}$, $R=\left(\frac{\ell_{1}-\ell_{2}}{\ell_{2}}\right) R$. If the driver cell of emf 5V is replaced with a cell of 2V keeping all other factors constant then potential drop along AB is 0.2Volt. Measurement of emf of commercial cells using digital potentiometer, (Rate this solution on a scale of 1-5 below), Log into your existing Transtutors account. Circuit diagram of potentiometer Potentiometer consists of a long resistive wire AB of length L (about 6m to 10 m long) made up of mangnine or constantan. Not quite correct to state that Potentiometer can measure EMF, it does not… Potentiometer is a misnomer as it is not a meter but just a variable resistance… Similarly the accuracy of a voltmeter reading is dependent upon on what kind of … A potentiometer is an instrument for measuring voltage or 'potential difference' by comparison of an unknown voltage with a known reference voltage. Find E1/E2. To measure a cell's emf a potentiometer is used since in a potentiometer measurement no current is flowing. And also it is used to compare the EMFs of different cells. If unknown emf $\mathrm{E}_{1}$ is balanced at length $\ell_{1}$ then $E_{1}=x \ell_{1}=\left(\frac{E_{0}}{\ell_{0}}\right) \ell_{1}$. Browse More Topics Related to Potentiometer: Let $E_{1}$ emf be balanced at length $\ell_{1}$ and $E_{2}$ emf be balanced at length $\ell_{2}$ then, $E_{1}=x \ell_{1}$ and $E_{2}=x \ell_{2}$ so $\frac{E_{1}}{E_{2}}=\frac{l_{1}}{l_{2}}$, If two cells joined in series support each other, If two cells joined in series oppose each other. Difference Between Potentiometer & Voltmeter The potentiometer and the voltmeter both are the voltage measuring device.The significant difference between the two is that the potentiometer measures the emf of the circuit whereas voltmeter measures the end terminal voltage of the circuit. Apparatus: a potentiometer , a battery , (or eliminator ) , two one way key , a rheostat of low resistance , a galvanometer , a high resistance box , a fractional resistance box , an ammeter , a voltmeter , a cell , a jockey , a set square , connecting wires , a piece of sand paper . The emf of a cell may be defined as the terminal voltage of the cell when not under load, that is, delivering no current. where E1 and E2 are EMFs of two cells, l1 and l2 are the balancing lengths when E1 and E2 are connected to the circuit respectively and φ is the potential gradient along the potentiometer wire. 0 A. C. 2 A. A voltmeter cannot be used to measure the emf of a cell because a voltmeter draws some current from the cell. The terminal voltage of a cell is the potential difference between its terminals. it uses null method so that no current is drawn from cell in balanced condition, as E – Ir = V and I = 0 then V = E. hence emf measurement is more accurate. 0.2 $\Omega / m$. E 1 is connected to end A and a negative terminal is … APPARATUS: Slide wire potentiometer, battery or power supply, rheostat, double pole-double throw (DPDT) switch, standard cell, unknown cell, galvanometer, key switch and a multimeter. It is also used to measure the internal resistance of a given cell. Get plagiarism-free solution within 48 hours, Your solution is just a click away! Since the reference voltage can be produced from an accurately calibrated voltage divider, a potentiometer can provide high precision in … Ask a Similar Question. Hence V=IR = E-Ir Dr. D. K. Pandey Internal resistance by potentiometer Object: To determine the internal resistance of Leclanche cell using potentiometer. The Potentiometer is an electric instrument used to measure the EMF (electromotive force) of a given cell, the internal resistance of a cell. Potentiometer works on the principle that when a constant current flows through a wire of uniform cross sectional area, potential difference between its two points is directly proportional to the length of the wire between the two points. or numbers? A voltmeter cannot be used to measure the emf of a cell because a voltmeter draws some current from the cell. 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